Automated characterization of dextran/concanavalin A mixtures—A study of sensitivity and temperature dependence at low viscosity as basis for an implantable glucose sensor

Mixtures of aqueous solutions of dextran and concanavalin A have a potential use as glucose sensing substances. We investigate these mixtures at low viscosities which are especially advantageous for miniature mechanical glucose sensing devices. The glucose dependent viscosity variations were studied in the range of 5–290 mPas and 20–40 °°C. The measurements were performed in a glass Ubbelohde viscometer, combined to a camera read-out device and two syringe pumps to inject glucose and to load the sample. The accuracy obtained with that system is better than ±±0.6% and allows a fully automated viscosity characterization of the solution. The measured sensitivity is particularly good at lower glucose concentrations (<<7 mM), which is the normal physiological range. The results showed that low-viscous mixtures, down to 5 mPas, are well suited for glycemic sensing applications. The viscosity of the mixtures is strongly dependent on the temperature (typically 3–7% per °°C), indicating that one needs to measure the temperature of the liquid, to obtain the accuracy required for in vivo glucose sensing.